1. Field of the Invention
Embodiments of the invention generally relate to the field of semiconductor manufacturing processes and devices, more particular, to methods of implanting ions into a substrate by a plasma immersion ion implantation process.
2. Description of the Related Art
Integrated circuits may include more than one million micro-electronic field effect transistors (e.g., complementary metal-oxide-semiconductor (CMOS) field effect transistors) that are formed on a substrate (e.g., semiconductor wafer) and cooperate to perform various functions within the circuit. A CMOS transistor comprises a gate structure disposed between source and drain regions that are formed in the substrate. The gate structure generally comprises a gate electrode and a gate dielectric layer. The gate electrode is disposed over the gate dielectric layer to control a flow of charge carriers in a channel region formed between the drain and source regions beneath the gate dielectric layer.
An ion implantation process is typically utilized to implant and dope ions into the substrate, forming the gate and source drain structure with desired profile and concentration on the substrate. During an ion implantation process, different process gases or gas mixtures may be used to provide ion source species. As the process gases supplied into the ion implantation processing chamber, a RF power may be generated to produce a plasma to promote ion dissociation in the process gases and accelerate the dissociated ions toward and into the surface of the substrate. As ions accelerated to the substrate surface are typically in a linear movement, e.g., one directional movement, the ions are mostly implanted into a bottom surface of a structure, e.g., patterns or trenches, formed on the substrate surface rather than to sidewalls of the structure. Non-conformal ion doping may result in insufficient and/or non-uniform ion concentration, profile, dimension, and distribution across the substrate surface, thereby adversely affecting the overall electrical device performance. As critical dimensions shrink, the precision of ion implantation becomes increasingly important.
Therefore, there is a need for an improved ion implantation process.